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# Guide for Population-Genetics Problems using the Hardy-Weinberg Equilibrium.

In a particular flower, a single pair of alleles determines the petal color (C). Red flowers have the genotype CR/CR (homozygous for CR), white flowers have the genotype Cr/Cr (homozygous for Cr) and pink flowers have the genotype CR/Cr (they are heterozygous).

In a given population, 49 flowers had red petals, 42 had pink petals and 9 had white petals. What are the frequencies of the CR and Cr alleles?

#### Solution Preview

Guide for Population-Genetics Problems and the Hardy-Weinberg Equilibrium

The best way to master population genetics is to work through as many problems as possible. This information should help you get started.

1) Allelic frequencies

The frequency of alleles in a population can be expressed as a number.
Suppose we have 100 alleles of a particular gene in a population, with 70 of these being allele R and 30 being allele r.

Frequency of R = 70/100 = 0.7 or 70%
Frequency of r = 30/100 = 0.3 or 30%

2) Calculating the allelic frequencies in alleles showing intermediate inheritance.

Problem

In a particular flower, a single pair of alleles determines the petal color (C). Red flowers have the genotype CR/CR (homozygous for CR), white flowers have the genotype Cr/Cr (homozygous for Cr) and pink flowers have the genotype CR/Cr (they are heterozygous).

In a given population, 49 flowers had red petals, 42 had pink petals and 9 had white petals. What are the frequencies of the CR and Cr alleles?

Solution

The total number of flowers in the population is 49 + 42 + 9 = 100.
Since each flower has two alleles, the total number of alleles in the population is
2 x 100 = 200.

Each of the 49 red ...

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